\chapter{Test study of technologies}

This chapter covers the experimental research conducted during the project. A reduced network model that does not have a direct mapping with the real DAS-4 network was used. However, the model still provides enough machines and network redundancy for all test cases related to capacity provisioning and dynamic reconfiguration.

First, a description of the test setup is given. Next, test cases are their traffic patterns are explained. Finally, results are presented per type of topology and protocol. The chapter is concluded with a discussion of results.

\section{Testbed specification}

The created testbed includes three servers (TODO ref appendix) with one managed switch (TODO ref appendix). As the managed switch supports up to 100Mbps line speed, the interfaces of the used servers were reduced from 1Gbps to 100Mbps by removing auto negotiation and hard-setting their speed and duplex settings. Each test was conducted twice - first in a stable environment without any link reconfiguration and then in a dynamic environment in which reconfigurations occur. Simulating link reconfiguration was performed by changing the VLAN membership of ports on the switch that connect to the network interfaces of a particular pair of servers. An overview of the setup is shown in Fig. x. 


\begin{figure}[h]
	%\begin{center}
			\includegraphics[width=4.7in]{/home/madave/Dropbox/school/RP2/das4-routing/report/figures/testTopBase.jpg} 
	%\end{center}
	\caption{Test topology physical setup}
\end{figure}
\vskip2em

All routers in the test topology are equipped with three physical network interfaces. These interfaces were used for connecting to the switch. Host nodes, however, were implemented as XEN virtual machines running on the routers themselves and each connects to a virtual bridge. This was done due to a shortage of available network interfaces on the routers in addition to PCI expansion slots. The IP addressing on each segment containing a virtual bridge and a host node remained static throughout all tests. Inter-router links on the other hand, used a dynamic addressing plan in conformance with the particular test that was run. 

Host nodes in the setup represent DAS-4's clusters. In the real environment, router interfaces on each cluster segment offer 10Gbps bandwidth, making it impossible to take advantage of bandwidths higher that 10Gbps between a pair of clusters. This is because higher capacity provisioning in the network is only used to facilitate network configurations in which lightpath limitation assignment places two transmitting clusters one behind the other towards their mutual network traffic endpoint cluster.

Therefore, all tests were conducted by using parallel transfers from two different hosts towards a third one. That  way, there is always one intermediate router, given careful topology selection, that would have to process more that the bandwidth capacity offered to the local cluster. 


\section{Test methodology}

Three important groups of statistics were gathered:

\begin{itemize}
    \item I/O counter tracking on all multiple inter-router interfaces
    \item Throughput, round-trip delay, loss rate and retransmits for a single and multiple TCP connections
\end{itemize}

The latter four tests were chosen due to limitations characteristic presented by ECMP and MPTCP (TODO: back this up in previous chapter explicitly). Two traffic patterns were used during tests: one for testing the performance of a single TCP connection and another for testing multiple TCP connections. However, in the case of the latter, all TCP connections were established only between  the same pair of machines. The real network traffic patterns in the DAS-4 network may be vastly different than the ones used during testing. For example, depending on the running applications, nodes from different clusters may be communicating in pairs or sets of a higher degree between one another.

- single connection throughput testing
- traffic patterns between the clusters?
- important traffic patterns for the DAS-4 cluster
    - single load from one mpeer
        - how is traffic distributed?
    - parallel load from multiple peers



\section{Static topology tests}

\subsection{Link aggregation}

As the currently used capacity provisioning technology in the DAS-4 network, LACP was used as a baseline against which to compare data obtained from other protocols. Fig. x shows the used topology:

\begin{figure}[h]
	%\begin{center}
			\includegraphics[width=4.7in]{/home/madave/Dropbox/school/RP2/das4-routing/report/figures/LACPStatic.jpg} 
	%\end{center}
	\caption{Test topology physical setup}
\end{figure}
\vskip2em

All interfaces in the topology are 100Mbps with the bond link being 200Mbps. Traffic generation was performed by using two simultaneuos \emhp{iperf} transfers from hosts 1 and 3 towards host 2 with all traffic captures performed on host 2.

\subsection{Bi-directional load-balancing}

\subsection{Multipath TCP}

\subsection{Static topology tests summary}

\section{Dynamic topology tests}

\subsection{Link aggregation}

\subsection{Bi-directional load-balancing}

\subsection{Multipath TCP}

\subsection{Dynamic topology tests summary}

throughput
latency
jitter
loss rate
out-of-order



\section{Routing}



Avaliable linux technologies:
- quagga
    - on-
- bird
    - 

